Robotic stations with self-teaching functions are known in the art. One of the most time-consuming and difficult tasks in connection with the use of robotic stations is a robot arm with End of Arm Tools (EOAT), such as edge grippers, or end effectors for moving along a preprogrammed rout with high accuracy on each working cycle.
A large automated robotic station may have a plurality of points that must be manually taught. The operator moves a robot's end effector through a required number of degrees of freedom to align the end effector within an acceptable tolerance to given picking/placing/processing positions. The speed and accuracy of this operation depends on such factors as experience, fatigue, visual acuity of the robot operator, etc. Even though the teaching process is accurate, reliability of the robot operation may also depend on plays in connections of the tooling and end effectors to the robot arm and on slack accumulated after a certain amount of the performed cycles. Consequently, such taught points often need to be refined by the robot operator one or more times to increase the accuracy of the point.
The precision teaching allows accurate placement of delicate parts into cassette or other media, or on process chuck, etc., without damaging and/or rubbing walls thus reducing generation of particles and improving the yield.
Methods of teaching teachable robotic stations for handling and processing objects are known in the art and described in a number of patent publications.
For example, U.S. Pat. No. 5,297,238 discloses a method for calibrating a tool control frame (TCF) on a robot with respect to a known calibration reference claim (CRF), wherein the (CRF) is in rigid body relationship with a robot link. The method includes the steps of (a) attaching a sensory tool to the robot link, (b) calibrating the sensory tool with appropriate units of measurement, (c) identifying a calibration feature to be mapped by the sensory tool, (d) causing relative movement of the calibration feature within sensing range of the sensory tool, (e) recording robot configuration and pose as a first data record, (f) causing relative movement of the calibration feature and sensory tool along a known direction to a new position within sensing range, (g) recording configuration and pose as a second data record, and (h) applying coordinate transformations to the respective data records to generate a correct tool control frame (TCF) pose with respect to the (CRF).
U.S. Pat. No. 4,675,502 discloses a real time tracking control for taught path robots. A real time steering capability is provided to permit robot motion to be modified continuously in three dimensions as the robot is moving along a taught path. An arc welding robot or other taught path robot has a sensor located on the robot arm to sense the position of a desired path. The tracking control provides real time steering commands to the standard robot taught path and are calculated based on maintaining a constant, preprogrammed velocity along the desired path and coordination with the taught path.
U.S. Pat. No. 4,831,549 discloses a device and method for improving orientation and/or location accuracy of a programmable robot with respect to a target object. The method consists of calibrating the position of a terminal control frame associated with a robot end-effector which is coupled to a robot distal link. Separated reference positions external from the robot are identified, as to geometry and spatial data. This identification data is stored for later recall and comparison for use in determining a localized relative frame of reference. The robot end-effector is moved to a first reference position and a rigid body error correction is determined. This correction is stored in computer memory for application to later computer movement.
International Patent Application Publication WO 2010136961 discloses a method and a control device for controlling a robot having a robot arm with a number of individual arm sections, an end effector connected to one of the arm sections and a number of actuators for moving at least the end effector and at least one of the arm sections in at least two different modes of operation, i.e., a working mode and a training mode that corresponds to the working movements. The robot control device corrects the teaching position of the motion program stored in the storage, based on a change in the relative position obtained by the position calculator.
U.S. Pat. No. 8,242,730 discloses an automated robot teach tool and a method of use of the teach tool. The latter enables automatic teaching of pick and place positions for a robot. The automated robot teaches tool obviates the need for manual operation of the robot during the teaching. The result is an automated process that is much faster, more accurate, more repeatable and less taxing on a robot operator. The teach tool comprises: a body assembly with a proximity sensor mounted therein that is releasably mated with a robot end effector; a foot assembly coupled to the body assembly, wherein the foot assembly comprises a sensor target mounted therein that is located about the proximity sensor; and wherein the proximity sensor and the sensor target are configured to detect signals representative of a perturbation as the robot end effector moves the body assembly and foot assembly from a central position within a workpiece receptacle through six degrees of freedom. The aforementioned signals are used to determine a precise orientation for the robot end effector to pick up and place a workpiece to and from the workpiece receptacle. Signals representative of the perturbation are generated in response to the foot assembly colliding with a horizontal surface or a vertical surface of the workpiece receptacle.